Due to the restrictions of physical conditions, compared with a wired link, the transmission rate of a wireless link is relatively low, but the bit error rate is relatively high. When the Internet Protocol (IP) technology is applied in an environment of a wireless network cell, a problem that a packet header overhead is too large exists. For example, in an IPv6 voice communication packet, a packet payload truly required by a user often occupies only 22% of the entire packet, which not only wastes the bandwidth, but also increases the probability of the packet being discarded due to a packet error. If no efficient measure is taken, the wireless network resources are wasted, and meanwhile, the Quality of Service (QoS) is reduced.
By using a header compression mechanism, the forgoing problem may be solved, and at the same time, the inherent flexibility of the IP protocol may be guaranteed. The header compression mechanisms may include Robust Header Compression (ROHC), Real-time Transport Protocol Header Compression (CRTP), and Extended RTP Header Compression (ECRTP).
The ROHC, for example, is a flow-based header compression scheme. During network data transmission, most of the header domains of a packet in a same flow have the same values. In the ROHC mechanism, one packet is selected from a certain flow as a reference packet, and for other packets, only the information in the header domains that is different from the reference packet is sent, so as to achieve the compression purpose, thereby saving the packet header overhead, and utilizing the bandwidth more efficiently. Meanwhile, the ROHC mechanism ensures high effectiveness and proper robustness by controlling the frequency and quantity of feedback messages, and detecting logic that is not synchronized, and through error check. Therefore, the ROHC mechanism provides a header compression mechanism that applies to a link with a high bit error rate and a long delay.
The ROHC mechanism has certain universality, and applies to various networks. The packet format defined by the ROHC mechanism requires that each ROHC packet add a Context ID of the packet and each Initial and Refresh (IR) packet and Initial and refresh-Dynamic (IR-DYN) packet add a Profile ID of the packet.
The inventor finds that, during data transmission, if each ROHC packet carries a Context ID and/or a Profile ID, data redundancy occurs, thereby wasting network transmission resources.